Double grating three dimensional spectrograph

• US 20030048442A1
• Filed: 09/07/2001
• Published: 03/13/2003
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Horiba Instruments Incorporated (Horiba Limited)
• Original Assignee: Jian Ming Xiao
• Inventors: Xiao, Jian Ming
• Granted Patent: US 6,952,260 B2
• Time in Patent Office: Days
• US Class Current: 356/328
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/04 Slit arrangements slit adjustment
• CPC Class Codes: G01J 3/18 using diffraction elements, e.g. grating gratings per se G02B

Abstract

A spectrograph with a first concave spectrographic diffraction grating is positioned to receive light from the input light source is configured to provide a diffracted light output dispersing the components of the input light source in a first direction. The dispersion forms the input light into an intermediate spectra. The intermediate spectra is formed in a focal surface by the once diffracted light. A slit is substantially positioned on the focal surface. A second concave diffraction grating is positioned to receive once diffracted light from the slit and configured to provide a twice diffracted light output, the second concave diffraction grating dispersing the components of the input light source in a second direction. The second direction is different from the first direction, the dispersion forming the input light into an output spectra.

Claims

1. A device for separating light into its components providing a light output in a selected spectral band from a sample light input into the device for separating light into its components, comprising:

(a) an input light source;

(b) a first concave spectrographic diffraction grating positioned to receive light from said input light source and configured to provide a diffracted light output dispersing the components of said input light source in a first direction, said dispersion forming said input light into an intermediate spectra, said intermediate spectra being formed in a focal surface by said once diffracted light;

(c) a slit substantially positioned on said focal surface or approximately on said focal surface, said slit having a first edge whose position corresponds to the shortest wavelength for light to be passed by said slit and having a second edge whose position corresponds to the longest wavelength for light to be passed by said slit; and

(d) a second concave diffraction grating positioned to receive once diffracted light from said slit and configured to provide a twice diffracted light output, said second concave diffraction grating dispersing the components of said input light source in a second direction, said second direction being different from said first direction, said dispersion forming said input light into an output spectra, said output spectra being formed on a focal surface by said twice diffracted light.

2. A device for separating light into its components as in claim 1, wherein said spectrographic grating is a monochromator type grating.

3. A device for separating light into its components as in claim 1, further comprising a movable member supporting said slit at a plurality of positions with said first and second edges that positions corresponding to the shortest and longest wavelength in a range of wavelengths to be selected by said slit.

4. A device for separating light into its components as in claim 1, further comprising a recording member positioned substantially along the focal surface of said second concave diffraction grating.

5. A device for separating light into its components as in claim 1, further comprising a measuring device positioned substantially along the focal surface of said second concave diffraction grating.

6. A device for separating light into its components as in claim 5, wherein said measuring device is a solid-state detector array.

7. A device for separating light into its components as in claim 1, further comprising a rotary mounting for rotatably supporting said first concave diffraction grating.

8. A device for separating light into its components as in claim 1, further comprising a rotary mounting for rotatably supporting said second concave diffraction grating.

9. A device for separating light into its components as in claim 1, further comprising a first rotary mounting for rotatably supporting said first concave diffraction grating and a second rotary mounting for rotatably supporting said second concave diffraction grating.

10. A device for separating light into its components according to claim 4, wherein said recording member is a light sensitive member.

11. A device for separating light into its components according to claim 1 wherein said input light source comprises a fiber optic bundle disposed at said light aperture.

12. A device for separating light into its components according to claim 1 wherein said second grating has a diameter at least two times greater then said height of said slit.

13. A device for separating light into its components according to claim 1 wherein said first and second grating have a diameter of 3 mm or higher.

14. A device for separating light into its components according to claim 1 wherein said first and second directions are substantially perpendicular to each other.

15. A device for separating light into its components according to claim 1 operable at wavelengths in a range of 180 nm to 10 um.

16. A device for separating light into its components according to claim 1 wherein stray light rejection is in the order of 10⁻

5 to 10<sup>−

6</sup>.

17. A device for separating light into its components according to claim 1 wherein said first and second grating have a groove density of 80/mm or higher.

18. A device for separating light into its components according to claim 1 wherein said second direction is substantially perpendicular to said first direction.

19. A device for separating light into its components according to claim 1 wherein the width of said slit determines the range of a spectral segment.